IMPROVEMENTS RELATING TO COMPONENT MOUNTING ARRANGEMENTS

Abstract: Mounting arrangement for mounting an electrical component on a printed circuit board. The component is provided with at least one electrical terminal pin which extends in parallel relationship with conductive legs projecting from an underside of the component. The terminal pin is so spaced from the legs and so shaped or profiled that it is deflected laterally from the normal position thereof as it moves into a plated through-hole in the printed circuit board while the conductive legs slidingly engage respective further plated through-holes. The shaping of the terminal pin allows the pin to return to its normal position relative to the conductive legs and thereby co-operate with the printed circuit board to retain the component securely in position when the component becomes fully mounted.

Description: IMPROVEMENTS RELATING TO COMPONENT MOUNTING ARRANGEMENTS This invention relates to component mounting arrangements for the secure mounting " of electrical components on printed circuit or wiring boards prior to the automatic soldering of the components to such boards. The present invention is especially, but not exclusively applicable, to the secure mounting of an RF electrical connector on a printed circuit or wiring board prior to the soldering of the terminals of the connector to conductive elements (e.g. tracks) of the printed or wiring board. Such connector or other electrical component may comprise an array of metal terminal members projecting orthogonally in parallel from an undersurface of the component body. The terminal members are arranged to extend through appertaining plated-through holes formed in a printed circuit board as the component is mounted on the board in readiness for subsequent soldering of the component terminal members to conductive tracks on the board contiguous with the plated-through holes. It is important that the electrical component or components are securely mounted on the board during the component assembly procedure to prevent the components from becoming dislodged, or even separated, from the printed board (e.g. as by tilting) before and/or during an automatic soldering process for soldering the components to the printed board. It has hitherto been proposed to provide the terminal legs of an RF electrical connector with integral barbs or the like which serve to bite into the plating of appertaining plated-through holes in the board, as the terminal legs are pressed therethrough, for the secure mounting of the connector on the board. Such arrangements for securely mounting a connector on the board prior to automatic soldering suffers from the disadvantage that the plating of the plated through-holes may be damaged by the barbs as the connector is pressed down on to the board, particularly in view of the manufacturing tolerances which give rise to variations in the plated hole and/or barb dimensions. Moreover, the barbs make it very difficult to remove the connector from the board without serious damage being caused to the plated through-holes, once a component has been mounted on the board in readiness for soldering, such removal sometimes being necessary due to the mounting of the wrong connector on the board or to the mounting of the connector at an incorrect location on the board. In accordance with the present invention there is provided a mounting arrangement for securely mounting an electrical component on a printed circuit or wiring board prior to the soldering of component terminal means to conductive elements (e.g. tracks) on the board contiguous with one or more of a plurality of plated-through holes extending through the board for slidingly receiving respective conductive legs projecting from an underside of the component, in which the electrical component is provided with at least one electrical terminal pin or contact which extends in parallel relationship with the conductive legs and which is spaced from the conductive legs and shaped or profiled so that the terminal pin is deflected laterally from a normal position thereof as it moves into a further plated through-hole in the printed circuit or wiring board while the conductive legs slidingly engage their respective plated through-holes and in which the shaping or profiling of the terminal pin allows the terminal pin to resume, at least substantially, its normal position relative to the conductive legs and thereby co-operate with the printed circuit board to retain the component securely in position when the component becomes fully mounted. To facilitate deflection of the terminal pin the pin will be offset from the appertaining plated-through hole in the printed board and such offset is preferably achieved by arranging that the plated-through holes for mounting the component are symmetrically arranged whereas the terminal pin is slightly asymmetrically disposed relative to the conductive legs of the component. In carrying out the present invention the resumption of the terminal pin of the component to its normal position may occur suddenly as the component is pressed down, in order to provide a positive snap action. The deflection of the terminal pin of the component on insertion of the pin into the appertaining plated through-hole may be permitted due to the inherent resilience of the terminal pin itself and/or the inherent resilience of an insulating support member for the terminal pin. The terminal pin or contact may be profiled by providing it with a cone-shaped enlarged head portion at its free end. In cases where the printed circuit or wiring board is of a standard thickness the rear end of the cone shaped-head portion may present a radially extending annular shoulder a substantial part of which abuts against the under surface of the printed circuit board to hold the component securely when the pin resumes its normal position after fully mounting of the component on the board. In cases where the printed circuit board or wiring board is of non-standard thickness the cone-shaped enlarged head portion of the terminal pin may be preceded by an oppositely-tapered conical section which allows the terminal pin to resume substantially its normal non-deflected position once the head of the terminal pin has passed through the appertaining plated-through hole of the printed board. The present invention is particularly applicable to an RF electrical connector the centrally disposed terminal pin or contact of which having the cone-shaped head portion will be connected or connectible to the central conductor of a coaxial cable while the conductive legs of the connector will be connected to the metal body of the connector connected to the braided sheath of the coaxial cable for grounding purposes. The RF electrical connector may simply comprise a rectangular (e.g. square) apertured base member from the underside of which four terminal legs defining a square leg array extend in parallel relationship. The apertured base of the connector may have a hollow cylindrical body part extending upwards therefrom for receiving the end of a coaxial cable and embodying a dielectric bush through which extends a central terminal pin or contact for connection at the upper end thereof to the central conductor of the coaxial cable and for insertion at its lower end, provided with a cone-shaped head portion, through a plated hole in the printed circuit board. The axis of this terminal pin or contact is slightly offset from the centre of the square terminal leg array. In another embodiment of the invention as applied to an RF connector, the base of the connector comprises a rectangular block having a cylindrical aperture therein from the underside of which four terminal legs project in parallel relationship. The block has extending from the base thereof a central terminal pin or contact which is supported in a dielectric bush and provided with a cone-shaped head portion. However, in this case the block has a laterally- extending hollow cylindrical body part the weight of which would tend to cause the connector to tilt when mounted on a printed circuit board without the secure mounting arrangement provided by the present invention by which a deflectable suitably-shaped electrical terminal extends from the block base in parallel with but slightly offset from the centre of the rectangular leg array and connectible with the central conductor of a coaxial cable. By way of example the present invention will now be described with reference to the accompanying drawings in which: - Figure 1 shows an enlarged perspective view of one embodiment of an RF electrical connector according to the invention prior to the mounting thereof on a printed circuit board with parts of the connector and printed circuit board being cut away; Figure 2 is a diagrammatic underneath view of the connector of Figure 1 showing the normal positional relationship between terminals of the connector before and after the mounting thereof on the printed circuit board; Figure 3 is a perspective view of another embodiment of an RF electrical connector according to the invention prior to the mounting thereof on a printed circuit board; and, Figure 4 is a diagrammatic underneath view of the connector of Figure 3 showing the normal positional relationship between terminals of the connector before and after the mounting thereof on the printed circuit board. Referring to Figure 1, there is shown an RF electrical connector 1 before the mounting thereof on a printed circuit board 2. The connector comprises an apertured metal body formed by an apertured square base 3 having an integral hollow cylindrical part 4 extending upwards therefrom. The through passageway provided by the apertured connector body accommodates an insulating bush 5 of dielectric material. An electrical pin terminal 6 extends through and is supported by the bush 5. The upper end 7 of the pin terminal 6 which projects into a cavity 8 in the bush 5 will be electrically connected to the central conductor of a coaxial cable (not shown) with the usual external braiding of the cable being electrically connected to the metal body of the connector for grounding purposes. The lower end 9 of the pin terminal 6 projects orthogonally from the underside of the square base 3 of the connector body. The base 3 has four metal terminal legs 10, 11, 12 and 13 defining a square terminal leg array, as can best be seen in Figure 2. These terminal legs are shown as being of square cross section but they may be of any other suitable shape and are positioned and dimensioned to fit slidingly into four plated-through printed circuit board holes, three of which are shown at 14, 15 and 16 in Figure 1. The printed circuit board 2 for mounting the connector 1 also has a plated-through hole 17 located centrally relative to the other four plated-through holes. The hole 17 is for slidingly receiving the lower end 9 of the pin terminal 6 projecting downwardly from the connector body part 3. In accordance with the invention ϊthe axis of the lower projecting end 9 of the terminal pin 6 is offset slightly from the centre of the square leg array, as can clearly be seen in Figure 2. At the same time the projecting end 9 of the terminal pin 6 is provided with a cone-shaped head portion 18 and the pin is deflectable laterally, such as due to the resilience of the dielectric material of the supporting bush 5 and/or the inherent resilience of the terminal pin metal. The part 19 of the terminal pin immediately above or preceding the head portion 18 is of substantially reduced diameter cylindrical configuration so that the head portion 18 presents an upwardly facing annular shoulder 20. In order to mount the connector 1 on the board 2 the connector will be located relative to the board so that the terminal legs 10, 11, 12 and 13 of the connector are brought into registration with and then enter the appertaining holes in the board as the connector is pressed downwards . Although the lower projecting end 9 of the terminal pin 6 is offset relative to the centre of the square terminal leg array (see Figure 2) so that the pin axis is also offset from the axis of the plated-through hole 17, the narrow tapered end of the cone-shaped head portion 18 nevertheless enters and moves downwardly into the hole 17 as pressure is applied to the connector body. However, as the cone-shaped head 18 moves progressively down into the hole 17 the projecting end 9 of the terminal pin will be deflected to one side, as permitted by the resilience of the supporting bush 5 and/or the metal of the terminal pin 6, until the head portion 18 moves out of the bottom end of the board hole 17 whereupon the terminal pin end 9 suddenly resumes its original non-deflected position by a lateral snap displacement of the end 9 so that a substantial part of the shoulder 20 engages the undersurface of the printed circuit board 2 and the connector is effectively securely locked to the board. Such locking action or secure mounting of the connector 1 on the board 2 prevents the connector from becoming dislodged or even being separated from the printed circuit board before or during subsequent automatic soldering of the connector terminals to conductive tracks (not shown) on the board contiguous with the plated-through holes. However, if for any reason it becomes necessary to remove the connector 1 from the board 2 before soldering, the pin terminal end 9 can readily be deflected laterally in order to allow withdrawal of the connector from the board. Referring now to Figures 3 and 4 of the drawings which illustrate a different embodiment of the invention, in this case a connector 21 comprises a metal body formed by a rectangular block structure 22 provided with internal generally cylindrical cavities 23 and 24 located at right- angles to one another. The cavity 24 is effectively extended by a cylindrical cavity (not shown) in a laterally extending hollow cylindrical metal body part 25. The connector embodies a generally centrally disposed terminal pin 26 which has a downwardly extending portion 27 which is insulatingly supported within the metal block structure 22 of the connector by means of an insulating bush 28 of dielectric material . The connector has four terminal legs 29, 30, 31 and 32 which are shown as being of square cross section, as can best be seen in Figure 4. These terminal legs which could be of any other suitable cross-sectional shape project downwardly from the base 22 in parallel relationship and define a square terminal leg array. The terminal legs are designed to be slidingly received by respective appertaining plated-through holes, three of which are shown at 33, 34 and 35, in a printed circuit board 36. As will readily be appreciated, the connector 22, unlike the connector 1 of Figures 1 and 2, is of asymmetrical configuration as a consequence of which the connector would have a considerably greater tendency to tilt to cause partial withdrawal or dislodgement of at least two of the terminal legs from their respective holes in the printed circuit board 36 when the connector is mounted on the board prior to and/or during automatic soldering of the board, unless the connector mounting is secure. In accordance with the invention the terminal pin 26 is provided at its lower end with a cone-shaped head portion 37 similar to that of the Figure 1 embodiment. However, in the case of the present embodiment an oppositely tapered conical section 38 is provided immediately above or preceding the cone-shaped head portion 37. This allows for variations in the thickness of the printed circuit board 36, as hereinafter will be apparent . To mount the connector 21 on the printed circuit board 36 which also has a centrally-disposed plated-through hole 39 for receiving the terminal pin 26, the terminal legs, as in the case of Figure 1, are moved into registration with their appertaining plated-through holes. Pressure is then applied to the connector so that the lowermost narrow-tapered end of the cone-shaped head portion 37 enters the hole 39. Due to the pin 26 being offset from the centre of the terminal leg square array, as can be seen in Figure 4, the lower projecting end of the pin 26 will then be deflected to one side against the resilience of the pin metal and/or the resilience of the material of the bush 28 as the cone-shaped head portion 37 travels down through- the hole 39. After the cone-shaped head portion 37 emerges from the bottom of the painted through-hole 39, the oppositely tapered portion 38 allows the laterally deflected projecting terminal pin end to restore progressively towards its original position as the pin end moves further, through the hole 39. As will be appreciated, the restoration of the terminal pin end in the case of this embodiment will not be as positive in providing the snap action mounting of the connector on the printed circuit board as in the Figure 1 embodiment, but the oppositely tapered section 38 does facilitate the use of the secure mounting arrangement of the invention with printed circuit or wiring boards of varying thicknesses. From the foregoing description it will be apparent that the secure mounting arrangement of the invention is especially applicable to the secure mounting of RF electrical connectors having central terminal pins and dependent terminal legs to printed circuit boards, but it will also be readily understood that the invention could possibly be applied to the secure mounting of other electrical components to printed circuit boards prior to the soldering of the components to the boards. It will also be understood that the invention embraces constructions of RF electrical connectors described herein for use in the mounting arrangement of the invention.

Claims: I 13 CLAIMS 1. A mounting arrangement for securely mounting an electrical component on a printed circuit or wiring board prior to the soldering of component terminal means to conductive elements (e.g. tracks) on the board contiguous with one or more of a plurality of plated-through holes extending through the board for slidingly receiving respective conductive legs projecting in parallel relationship from an underside of the component, in which the electrical component is provided with at least one electrical terminal pin or contact which extends in parallel relationship with the conductive legs and which is spaced from the conductive legs and shaped or profiled so that the terminal pin is deflected laterally from the normal position thereof as it moves into a further plated-through hole in the printed circuit or wiring board while the conductive legs slidingly engage their respective plated through holes and in which the shaping or profiling of the terminal pin allows the pin to resume, at least substantially, its normal position relative to the conductive legs and thereby co¬ operates with the printed circuit board to retain the component securely in position when the component becomes fully mounted. 2. A mounting arrangement as claimed in claim 1, in which the deflection of the terminal pin or contact during insertion of the pin into its appertaining plated-through hole is facilitated by the axis of the terminal pin being offset slightly from the centre of a symmetrical array of conductive legs while the plated through hole in the printed circuit board for receiving the terminal pin is centrally disposed relative to the array of plated-through holes for receiving the conductive legs. 3. A mounting arrangement as claimed in claim 1 or claim 2, in which the terminal pin is deflectable due to the resilience of the pin metal and/or of the insulating material of a pin support member. 4. A mounting arrangement as claimed in any preceding claim, in which the terminal pin is so shaped and dimensioned that the terminal pin resumes its normal non- deflected position suddenly to provide a positive snap action as the connector becomes fully mounted on the board. 5. A mounting arrangement as claimed in any preceding claim, in which the terminal pin is provided at the lower end thereof with an enlarged cone-shaped head portion which co-operates with the appertaining plated- through hole to produce deflection of the pin as it enters the hole. 6. A mounting arrangement as claimed in claim 5 as dependant on claim 3, in which the enlarged cone -shaped head portion presents to the rear thereof a radially- extending annular shoulder which abuts against the undersurface of the printed circuit board to lock the component to the board when the component becomes fully mounted on the board by the snap action. 7. A mounting arrangement as claimed in claim 5 as dependant on any of claims 1 to 3, in which the enlarged cone-shaped head portion has an oppositely tapered cone section immediately rearwards of it, the oppositely tapered cone section allowing the terminal pin to resume, at least substantially, its normal position after the head portion emerges from the appertaining plated through hole, irrespective of variations in thickness of the printed circuit board. 8. A mounting arrangement as claimed in any preceding claim, in which the electrical component comprises an electrical connector. 9. A mounting arrangement as claimed in claim 8, in which the electrical connector comprises an RF electrical connector with the usual central contact or pin for connection to the central conductor of the coaxial cable defining the deflectable terminal pin. 10. A mounting arrangement as claimed in claim 9, in which the connector comprises a body with a rectangular (e.g. square) apertured metal base structure from which projects a rectangular array of conductive legs in parallel relationship and in which the central terminal or contact of the connector which is supported by an insulating bush of dielectric material projects from the base in parallel with the conductive legs but the axis thereof is offset from the centre of the leg array. 11. A mounting arrangement as claimed in claim 10, in which the body of the connector is symmetrical. 12. A mounting arrangement as claimed in claim 10, in which the body of the connector has a part thereof extending laterally from the base structure to define an asymmetrical connector body. 13. An RF electrical connector for use in a mounting arrangement as claimed in any of claims 9 to 12. 14, A mounting arrangement for an RF electrical connector substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings. 15. An RF electrical constructed substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.

Inventors: BRUMWELL PETER JOHN, GRAY IAN JAMES STAFFORD, BRUMWELL, PETER, JOHN, GRAY, IAN, JAMES, STAFFORD
Applicants: ITT IND LTD, ITT INDUSTRIES LIMITED
Application year: 1994
Main classification: H05K13
IPC codes: H01R13, H05K3, H05K13